Wall mixer



FIG. 1 is a perspective view of a wall mixer according to my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof, the left side view being a mirror image thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof.

The views not shown form no part of the claimed design. 

CLAIM The ornamental design for a wall mixer, as shown and described. 